Pulse Ox Group:
infrared LEDs and red ones if they aren’t around driftmier
amplifier (haven’t decided on type yet)
photodiode
a sort of finger clamp that can hold the LED’s and photodiode onto the finger (might be able to construct something or 3D print it)

Also, I’d like you to decide which optoisolator you need. If you transmit a digital signal, we can use the 6N138. This means a bit more signal processing on the battery side. Or, you can build an analog mirror with a dual optoisolator, in which case I can offer the TLP620.

Pulse Oxymeter Group: You mentioned 3D printing. I think this is a great idea. Try to devise a sort of finger clip or finger sleeve onto which you can mount the electrooptics. This will help you a lot by making the signals more stable and less dependent on random movement.